1. Field of the Invention
This invention relates to a vibratory drum machine used especially for cleaning and cooling cast components to which the molding sand still adheres.
2. Description of the Prior Art
In FIG. 1, the vibratory drum machine of the prior art for cleaning and cooling the cast components is shown in general at 10. A support member 15 is fixed through strengthening ribs 26 to a cylindrical drum body 11. A mounting frame 12 is supported through springs 14 by the support member 15.
An inlet 25, into which the cast components to be cooled and cleaned are supplied, is formed at the left end portion of the cylindrical drum body 11 (FIG. 1). A discharge chute 24 is connected to the right end of the cylindrical drum body 11. The cooled and cleaned cast components are discharged outwards through the discharge chute 24. The left end of the drum body 11 is covered with an end wall 22a and the right end thereof is partially covered with an end wall 22b.
The drum body 11 is resiliently supported on the earth E by coil springs 16a, 16b, 17a and 17b. A drive source 13 consisting of a pair of vibratory electric motors 19a and 19b is fixed on the mounting frame 12. The vibratory electric motors 19a and 19b have well-known constructions. Nearly semi-circular unbalance weights 20a and 20b are fixed to rotary shafts 21a and 21b of the vibratory electric motors 19a and 19b. A reinforcing partition 23 is fixed to the center of the mounting frame 12. The vibratory electric motors 19a and 19b are fixed in symmetry on the mounting frame 12 with respect to the reinforcing partition 23. The unbalance weights 20a and 20b are rotated in the opposite directions, and they are fixed to the rotary shafts 21a and 21b in the same rotary phase. A dust collecting duct 18 is fixed on the upper wall portion of the drum body 11 and it communicates with an internal space 27 of the drum body 11. As described below, a dust generating in the cleaning and cooling operation of the cast components M is guided outwards through the dust collecting duct 18. The entire vibratory drum machine 10 is so arranged as to be inclined towards the discharge chute 24 by a few degrees.
When the drive source 13 is excited, the vibratory electric motors 19a and 19b are rotated in synchronization with each other. The pair of the vibratory electric motors 19a and 19b are driven at a frequency which is near to a resonance frequency. The resonance frequency is predetermined by a spring constant of the coil springs 14, and the masses of the entire drum body 11 and drive source 13. A linear vibratory force is generated in the direction along the coil springs 14. The vibratory force is transmitted to the drum body 11 through the coil springs 14 and support member 15. Since the drum body 11 is resiliently supported by the coil springs 16a, 16b, 17a and 17b, the drum body 11 is vibrated in an oblique direction as shown by a arrow A. Accordingly, the cast components M and sand S circulate as shown by the arrows in the internal space 27 of the drum body 11. The drum body 11 is inclined towards the discharge chute 24 by a few degrees. Accordingly, the cast components M and sand S are moved to the discharge chute 24 together with the circulation as shown by arrows in FIG. 2. In such a motion, the cast components M and sand S are separated from each other and they are discharged outwards through the discharge chute 24.
The vibratory drum machine 10 of the one prior art is so constructed as above described and operates in the above manner.
In a sand-separating machine of another prior art, a plate having plural slits is arranged and cast components to be cleaned and cooled are supplied onto the plate. It is vibrated in a linear direction. The sand separated from the cast components is discharged downwards through the plural slits and the cast components are moved on the plate by the linear vibratory motion. However, in this type sand-separating machine for the cast components, the cast components often are damaged by the shock. Further, some cast components freely can not move on the plate. Thus, some cast components are not be cleaned and cooled so much sufficiently according to their shape and the sands are not fallen from the cast components. On the other hand, the vibratory drum machine 10 of the above one prior art can remove the above described defects of the sand-separating machine.
Further, the pair of the vibratory electric motors 19a and 19b does not always synchronize with each other. When they are not synchronized with each other, some irregular vibratory force is imparted to the drum body 11. In that case, the above described operations are not effected and so the sands are not freely separated from the cast components. Further, the vibratory drum machine 10 of the one prior art has the same defect as the sand-separating machine as above described. For example, the cast components M sometimes are damaged on the internal wall of the drum body 11. To cope with this defect, the mounting position of the vibratory electric motors 19a and 19b to the drum body 11 and the arrangements of the coil springs 14 should be strictly designed so that the vibratory electric motors 19a and 19b can be rotated in synchronization with each other. Accordingly, the vibratory drum machine 10 of the one prior art as shown in FIG. 1 and FIG. 2 is much expensive and further the resonant condition can not be often obtained according to the sum weight of the supplied cast components M and sand S and their mass distribution. Accordingly, the synchronization of the rotation can not be often obtained.
In a sand-separating machine of a further type, a drum is rotated at a predetermined speed in a predetermined direction. It is so called "rotary drum". The cast components are brought up by engagement with members fixed on the internal wall of the drum and they are dropped out at some height. Accordingly, the cast components are often damaged on shock to the inside wall of the drum. Further, since contact time of the cast components with inside wall of the drum is long, the sand is often aged and also adding agent is often aged. Further, when the cast components are fallen onto the bottom portion of the drum, periodical noises are made. The vibratory drum machine of the one prior art is superior to this type sand-separating machine in the above defects. However, there are some points to be resolved as above described.
FIG. 3 and FIG. 4 show a vibratory drum machine of another type. Parts in FIG. 3 which correspond to those in FIG. 1 and FIG. 2, are denoted by the same reference numerals, the detailed description of which will be omitted. In this example, a vibratory force generating mechanism 13' for generating a linear vibratory force is mounted on the peripheral wall of the drum body 11. It consists of a pair of vibratory electric motors 22A and 22B. They are fixed on a mounting member 35. Gears 29a and 29b of the same diameter and the number of teeth are fixed on one end portion of the shafts 23a and 23b of the electric motors 22A and 22B. Gears 30a and 30b of smaller diameter are engaged with the gears 29a and 29b. The axes of the gears 30a and 30b are supported on a bearing housing 28. Electric power source cords 31 to an alternating power source are connected to the vibratory electric motors 22A and 22B. The electric motors 22A and 22B are driven in the opposite directions.
Substantially semi-circular unbalance weights 24a and 24b fixed to one end portions of the rotary shafts 23a and 23b are rotated at the same speed in synchronization with each other, and in the opposite directions through the engagements of the gears 30a, 30b and 29a, 29b. Thus a linear vibratory force is generated in a X direction as shown in FIG. 3.
Although, the vibratory drum machine 10' of the other type is constructed simply as above described and it has the following defects.
The drum body 11 of this type is in the shape of cylinder, too. And the cast components to be cooled and cleaned are moved along the central axis C of the drum body 11. It is supported resiliently by the coil springs 17a and 17b. Further, the vibratory exciter mechanism 13' consisting of the two vibratory electric motors 22A and 22B is fixed onto the peripheral wall of the drum body 11. Further also in this type, the substantially semi-circular unbalance weights 24a and 24b are fixed to the driving shafts 23a and 23b of the vibratory electric motors 22A and 22B. The gears of the same diameter and the same number of teeth are fixed to the one end portion of the driving shafts 23a and 23b and they are engaged with each other. Accordingly, the two vibratory electric motors 22A and 22B are rotated at the same speed in the opposite directions and in synchronization with each other. Thus, a linear vibratory force is generated in a direction P as shown by a arrow in FIG. 5. It intersects with the axis C of the drum body 11 at a right angle. When no cast components are supplied into the drum body 11, or when no load is applied to the drum body 11, different points on the peripheral wall of the drum body 11 are linearly moved as shown by the arrows in FIG. 5. The direction of the movement of the points on the peripheral wall are substantially parallel with the linear vibratory force direction P.
It makes an angle .alpha. relative to the horizontal line H--H at the peripheral position at which the vibratory force generating mechanism 13' is mounted on the peripheral wall of the drum body 11. Thus, the points on the peripheral wall of the drum body 11 are vibrated almost at the same amplitude and same vibratory angle.
When some cast components M to be cleaned and cooled are supplied into the drum body 11, the cast components M and sand S circulate as shown by the arrow in the same manner as above described prior art. However, the amplitudes of the points on the peripheral wall are greatly decreased in comparison with those in the no-load condition. Accordingly, actually the circulating motion as shown is difficult to be obtained, and further the circulating speed is decreased since the amplitude is smaller. Further, the fluidity is deteriorated in comparison with the above described prior art.
The reason for the above defect will be described. The cast components M to be cleaned and cooled are driven together with the drum body 11 in the vibratory direction P which is obtained under the no-load condition. The vibratory direction of the point on the bottom of the drum body 11 is substantially equal to the direction P as shown by the arrow a.sub.1 '. However at the angle portion a.sub.2 ' of 45 degrees in the counterclockwise direction, the vibratory directions of the points are substantially parallel to the direction P under the no-load condition. Accordingly, the direction of the vibration of the point at the angle 45.degree. is substantially parallel to the internal wall surface of the drum body 11 as shown by the arrow a.sub.2 '. Accordingly, it is clear from the theory of the vibration that the acceleration of the point in the vertical direction to the surface of the inside wall of the drum body 11 is smaller than 1 G. Accordingly, the cast components and sands can not jump from the wall surface of the drum body 11. The forward movement due to the vibration can not be imparted to the cast component and sands. Further, at a point of a larger angle, it is preferable to move the cast components and sands relative to the inside surface of the drum body 11 in the counterclockwise direction. However, actually the cast components and sands are moved in the clockwise direction. Accordingly, the movement of the cast components and sands at the larger angle position a.sub.3 ' is opposed to the movement of the cast components and sands at the lowest point a.sub.1 '. Thus, the cast components M and sands S separated from the cast components M push the inside wall surface of the drum body 11. As if the cast component M and sands S is integrated with the drum body 11 as a rigid body, they are vibrated as one body. Accordingly, it is natural that the amplitude of the different points on the peripheral wall of the drum body 11 are decreased and the fluidity is deteriorated as above described.
Further, in this prior art, the vibratory drum machine is driven, for example, at the power frequency of 60 Hz and vibrated at the rotational speed of 894 r.p.m. In the technical field of the vibration, the frequency of 894 r.p.m. belongs to the super low frequency zone. Accordingly, the houses which are adjacent to or near the vibratory drum machine are almost under a resonant condition of the super low frequency vibration. Thus, the houses and further the doors and desks are vibrated. A public nuisance is imparted to the people which live near the factory in which the above described vibratory drum machine is arranged.
Further, the gears are fixed to the driving shaft in the above described prior art. They are engaged with each other and they are rotated in the opposite directions. Even when the engagement with the gears is accurately designed, the engagement sound can not be zero. Further, the noise is in a high frequency zone. Such a noise is of a public noise nuisance to the people which live near the factory in which the vibratory drum machine is arranged.